1. Technical Field of the Invention
The present invention relates to a call back Subscriber feature in a telecommunications network and, in particular, to the use of an X.25/TCAP protocol converter for exchanging feature information between two telecommunications switches.
2. Description of Related Art
Developments and improvements in the telecommunications switching systems have allowed telecommunications subscribers to enjoy a vast number of high-level special subscriber features such as Class Automatic Callback (CAC) and Class Automatic Recall (CAR) provided by the Common Channel Signaling (CCS) Signaling System No. 7 (SS7) protocols. These subscriber features allow a first subscriber located in one switch to call back or recall a second subscriber located in another switch. If the second subscriber is already busy, the telecommunications network monitors the busy line until it goes idle and then establishes a connection between the first and the second subscribers. With the introduction of such subscriber features, subscribers do not have to repeatedly dial their busy calling parties' numbers until a connection is established or even have to know the telephone number of the party the subscriber has lastly spoke with. However, even though these subscriber features have overcome technical hurdles and allowed the first subscriber to merely enter a service code and wait for the network to call him back when the second subscriber goes idle, the features still cannot overcome politically placed telecommunications hurdles.
These hurdles or restrictions are usually placed by a local government for political or religious reasons and do not allow Signaling System No. 7 (SS7) or Channel Associate (CAS) signaling on the outbound traffic if the calls are directed toward certain "undesirable" countries. Accordingly, these restrictions imply that outbound SS7 calls to selected countries are not allowed, and only incoming SS7 calls are accepted. Therefore, if a telecommunications subscriber residing within a politically restricted telecommunication network area wishes to make a restricted outgoing international call, he or she would have to first call another switch placed in an unrestricted third country and then either manually or automatically relay that call to the desired restricted destination by having the third switch initiate a new call setup and transfer the call.
Therefore, it would be a desirable capability for a first telecommunications subscriber to place a call back request through a different network than the restricted SS7 telecommunications network and have the second telecommunications subscriber call back the first subscriber through the SS7 telecommunications network. Since only the outgoing calls are restricted toward certain countries, if the first subscriber can request the second subscriber to call back the first subscriber, the actual call back would constitute an incoming call for the restricted switch, and no restriction would bar this call setup.
It would also be another desirable capability for the same call back system to gain favorable international tariff charges by having a second subscriber residing in a favorable tariff country to call back a first subscriber residing in a less favorable tariff country. For example, since calling from Europe to the United States is always much more expensive than calling from the United States to Europe, if a first subscriber residing in Europe could order a call back request through an ubiquitous network and have a second subscriber residing in the United States call back the first subscriber through the SS7 telecommunications network, the actual call connection would be much less expensive for the first subscriber.
Accordingly, it is an enhancement and advantageous over the prior art because there is no longer the need to physically place a call toward a third country before establishing a connection with the desired party.